Your employer should have ceased withholding CT taxes as soon as you became a Florida resident. See this from the CT tax website:
"Example: Working solely outside Connecticut: A resident of New York works in New York for an employer whose main office, including the payroll department, is located in Connecticut. The employer is not required to withhold Connecticut income tax even though payment is made from a point in Connecticut, because the employee is a nonresident and performs all services outside Connecticut."
https://portal.ct.gov/DRS/Withholding-Taxes/Nonresidents-who-work-in-Connecticut
The CT "convenience rule" applies only if the taxpayer's resident state applies a similar rule for work performed for a CT employer. Since FL has no income tax, it obviously has no "convenience rule."
https://www.cga.ct.gov/2021/rpt/pdf/2021-R-0008.pdf
What you should do is file a part-year resident CT income tax return. On that return report your CT withholdings as shown on your year-end W-2, but allocate to CT only the income you earned while you were a resident of CT. This should result in CT refunding the excess withholding to you.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
